Learn How EPSOL Designed Ground Grid Using ETAP Software in a Steel Plant in Mexico

In this presentation, we will show you the procedure and use it to calculate the grounding system using the ETAP software and the finite element method. The proposed design was analyzed to determine whether the merged parameters meet the security conditions necessary for implementation.
By Carlos Moran Ramirez, Project Manager at EPSOL

In this case study, we learn about ground grid design in a steel plant in Mexico. The project's objective was to reduce the step and touch potentials in the area of ​​electric arc furnaces of 50 kA connected to transformers of 13.8/0.6 KV. When melting, they create dangerous currents for the workers who operate these furnaces. The project is executed from the field measurements of the resistivity of the ground and the design of the ground grid with the ETAP finite element method (FEM) and the construction of the grid is executed up to the foot of the ovens, thereby reducing said potentials to safe values ​​for the workers, contributing to a safer work area.

Epsol Energy & Power System serves the energy and power systems industry, providing services such as project management, construction of electrical substations, charging stations for electric vehicles, photovoltaic system integration, and compliance management with electrical interconnection standards. EPSOL provides the necessary expertise to deal with problems in the distribution and transmission of energy. Their solutions ensure continuity and reliability in the Electric Network.
Grupo Simec, S.A. de C.V. had steel mills and rolling facilities in Guadalajara, Jalisco, and Mexicali, Baja California, both dedicated to manufacturing commercial and structural steel long products, specialty steel bars, rebar, and steel beams. The conglomerate also has plants dedicated to fabricating special bar quality steels (SBQ), commercial structural long products, and rebar in Apizaco, Tlaxcala, and Cholula, Puebla.

Location: Puebla, Mexico

Year: 2022

Designing and building a grounding system for an old steel plant to ensure operator safety

Challenges

  • To find the procedure designers can use to calculate and analyze the grounding system for the old steel plant. The steel plant was rather old (built in the sixties), and the ground grid system used only steel rods (2 meters), working as ground cables.
  • Identify the actual rods and cables existing in the ground. The inventory should cover all areas around the steel plant and be used to analyze the existing system and make improvements.
  • To find a solution to upgrade the security for electrical maintenance service workers in the field.
  • The researcher should specify all grounding installation equipment needed for the new grounding solution and control the solution's cost.
  • Choose the right points to cover the measurements to measure the soil's resistivity. The iron dust covered the soil.
  • To meet the security conditions necessary for implementation in reality, the grounding system should be completely redesigned and customized according to the new law and standard.
  • To model the existing system with all the necessary characteristics and to propose a new one with new rod grids. To find all threats related to grounding.
  • To ensure the safe maintenance of the old steel plant.

Which solutions did they choose?

Selected applications

They have chosen the ETAP System Grounding and Earthing Analysis module to find the right grounding variations in these challenging conditions. The Ground Grid Systems module for ETAP enables engineers to quickly and accurately design, visualize, analyze and report ground protection projects of any size or complexity.

The ETAP solution guarantees compatibility with actual standards for electrical grounding systems in the steel industry. 

Why do they use ETAP?

Main Customer Benefits

  • Easy modeling of the existing grounding system with all characteristics from the field. All symbols have built-in electrical parameters. In ETAP, the process starts from the design and continues through the analysis, simulations, and build process.
  • Nineteen different points of the ground resistivity were measured and used in the virtual ETAP model. The short circuit analysis calculated a single-phase short circuit of 49,2 kA. Engineers could declare the surface type above the ground grid in the ETAP software, so the model was accurate enough to start calculations.
  • Special solutions in ETAP for Ground Grid Systems are dedicated to designing quickly and complexly. There is no need to use the other software.
  • A professional ETAP 3D visualization of the rod's configurations helped Epsol find a relevant solution and present it to its customer. This was important because the proposed solution used expensive copper.
  • Many specialized editors, such as the Soil Editor, Ground Resistivity Editor, Conductor Editor, Rod Editor, and, ultimately, Ground Study Editor, helped engineers work precisely and effectively.
  • Engineers can test the design by running the simulation in relation to the previous study about short circuits. Many graphs were generated, such as Absolute Potential, Touch Potential, and Step Potential Graph. The graphs use the full range of colors, which is useful during analysis and consultation with a customer. The report about grounding protection can be visualized in any browser, Word, CFD, or PDF.
  • Thanks to the ETAP analysis, they found many security problems, such as step and touch potentials. A step potential plot shows that the maximum voltage level is 848.5 volts, which any person walking 1 m away could experience. The Touch Potential graph found that the touch potential voltage level is critical and can be 3871.4 volts. This electrical potential exists when a person is in contact with the grounded structure in the substation.
  • Epsol engineers delivered analysis results in a comprehensible form (visualization, graphs, tables) to the customer, who approved what should be done. The ground grid was proposed to be made around the furnace building and the scrap site. Steel plant managers accepted the proposed design, and Epsol started to build.
  • The grounding's implementation used specifications made in the ETAP software. The grounding installation was about 1500 meters long and used large copper rods.
  • They achieved the desired ground resistance to prevent future problems. The steel plant became safe if we speak about grounding.

What do they think about ETAP?

Opinions

After registering the ground resistivity data, we started drawing the proposed grounding system. With the distance between rods and all the ground characteristics, ETAP helped us immensely, thanks to its wide range of wire sizes. There are also different types of rods to choose from.
By Carlos Moran Ramirez, Project Manager at EPSOL

ETAP also shows a 3D view of the ground grid, which helps imagine how the grid will be built. This helped us a lot while we were building the system.
By Carlos Moran Ramirez, Project Manager at EPSOL



Videos

Ground Grid Design with ETAP in a Steel Plant in Mexico - EPSOL

A Ground Grid design project is presented in a steel plant in Mexico and the objective is to reduce the step and touch potentials in the area of ​​electric arc furnaces of 50 kA connected to transformers of 13.8/0.6 KV and that in the moment of melting, they create dangerous currents for the workers who operate these furnaces. The project is executed from the field measurements of the resistivity of the ground and the design of the ground grid with the ETAP finite element method (FEM) and the construction of the grid is executed up to the foot of the ovens, thereby reducing said potentials to safe values ​​for the workers, contributing to a safer work area.


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